(Reuters) - The U.S. military said on Friday it was identifying new areas where it could work with allies to put pressure on Iran in support of President Donald Trump's new strategy, which promises a far more confrontational approach to Tehran.

Trump struck a blow against the 2015 Iran nuclear agreement on Friday in defiance of other world powers, choosing not to certify that Tehran is complying with the deal and warning he might ultimately terminate it. He also promised to address Iran more broadly, including its support for extremist groups in the Middle East.

Major Adrian Rankine-Galloway, a Defense Department spokesman, told Reuters the Pentagon was assessing the positioning of its forces as well as planning but offered few details.

"We are identifying new areas where we will work with allies to put pressure on the Iranian regime, neutralize its destabilizing influences, and constrain its aggressive power projection, particularly its support for terrorist groups and militants," he said.

The U.S. military has long been a strident critic of Iran, accusing it directly and indirectly of trying to undermine the United States and its allies, including in Iraq, Syria and Yemen. The tensions escalated in recent months in Syria, where American pilots shot down two Iranian-made drones this summer.

Still, a more aggressive approach to Iran could trigger a backlash from Iran's elite Islamic Revolutionary Guard Corps (IRGC) and forces that it backs. That includes in Iraq, where U.S. troops are fighting Islamic State and trying to keep their distance from Shi'ite militia aligned with Iran.

"U.S. forces in Iraq are quite exposed, and coalition forces are quite exposed to the risk of attack if Iranian elements so choose," said Jennifer Cafarella, lead intelligence planner at the Institute for the Study of War, a think-tank in Washington.

The U.S. military is analyzing an explosively formed penetrator, or EFP, that killed an American soldier in Iraq this month. The reappearance of the device, which Iran-backed Shi'ite militia routinely used to target American troops in Iraq before their withdrawal in 2011, has startled U.S. officials.

LINK TO IRAN?

CIA Director Mike Pompeo noted the device was detonated in an area controlled by a militia backed by Tehran. "We do not have evidence of a direct link to Iran, but we are closely examining this tragic incident," Pompeo said on Wednesday.

Cafarella said the killing of the U.S. soldier may have been a warning from Iran. "I think it is possible that the Iranians have been attempting to signal their commitment to retaliate against the U.S. strategy," she said.

Mattis, speaking to reporters traveling with him on Friday, said he had not yet seen any provocative actions from Iran following Trump's speech. "We keep an eye on the potential for more provocations from the Iranians but right now we have not seen that," he said.

Reuters has previously reported that options to increase pressure on Iran include more aggressive U.S. interceptions of Iranian arms shipments, such as those to Houthi rebels in Yemen. It could also direct U.S. naval forces to react more forcefully when harassed by armed IRGC speed boats.

The Pentagon on Friday detailed a series of major concern about Iran, including its ballistic missile development and cyber attacks against the United States and U.S. allies. The Pentagon promised to review U.S. security cooperation activities with allies in the region, something that could lead to alterations in U.S. arms sales and military exercises.

It also signaled a willingness to re-examine the positioning of the roughly 70,000 American troops the Pentagon says are stationed in the Middle East. Still, Mattis said: "Right now we are not changing our posture."